DESCRIPTION: The main hypothesis examined in this proposal is that the left hemisphere is specialized for processing high-frequency stimuli in vision and in audition, and that the right hemisphere is specialized for processing low-frequency stimuli in both modalities. Hemispheric specialization for different spatial frequencies in vision was proposed by Sergent, and the investigator and his collaborators have provided evidence that a parallel specialization may exit for sound frequencies. This proposal further examines the nature of asymmetric hemispheric specialization for high-frequency and low-frequency information in audition & in vision by examining auditory asymmetries in normal subjects (Experiments 1 and 2), auditory and visual asymmetries in patients with focal lesions (Experiments 3 and 4), crossmodal comparisons in normal subjects (Experiments 5, 6 and 7), and auditory asymmetries for speech perception in normal and patient groups (Experiments 8-11). In addition, a connectionist model of hemispheric asymmetries in vision and audition is proposed.